As the sizes and resolutions of displays of portable electronic devices have been increasing competitively, a demand for a function of a write input, a picture memo, or the like has been increasing accordingly. For example, functions of indicating a destination on a map, writing a message on a photo, and then transmitting the map or the photo or the like have become a main marketing point.
As a result, a user input for a specific function is sensed and a function corresponding to the sensed user input is conducted.
As a user input method, there is a method in which a user touches a user interface displayed on a display by a finger. However, when a write input is required as in Japan or China where Chinese characters are used, it is easy to conduct a picture or write input as well as being possible to enhance the accuracy thereof when a stylus pen (touch pen) rather than a finger is used. Thus, a touch function using a stylus pen is being magnified as an important factor in hardware differentiation.
The touch technique using a stylus pen can be generally classified into a pressure-sensitive method, an electrostatic method, a passive method, an active method, an electromagnetic resonance (EMR), and an electromagnetic induction method.
A pressure-sensitive pen is configured to conduct a touch or write input by applying pressure to a pressure-sensitive touch screen using a sharp tip. However, the usability of the touch screen itself is poor and there is no method of delivering the write pressure.
In addition, an electrostatic pen includes an elastic conductor (dielectric body) provided in a tip, and is configured to conduct a touch or write input by causing an electrostatic reaction on an electrostatic touch screen. Thus, there is no method for delivering the touch pressure.
Further, a passive type or active type pen merely substitutes for the role of a finger and it is impossible to differentiate a touch by the finger and a touch by the pen. Since the passive type or active type pen does not enable a proximity sensing function and a palm rejection function, an existing touch screen device cannot be used as it is unless a separate digitizer is used.
In addition, the passive type pen uses a thick tip having a thickness of 5 mm or more in order to generate an electrostatic capacity similar to that generated by a finger without using a separate battery or a coil. On the contrary, the active type pen is capable of generating an electrostatic capacity similar to that generated by a finger even if its tip is thin (2 mm) since it includes a battery or a coil built therein.
Meanwhile, an EMR type pen is capable of conducting an input through an electromagnetic induction reaction using an electromagnetic induction portion of a terminal and the pen since a terminal is configured to be active and the pen is configured to be passive. It is necessary to mount a digitizer within the touch screen device as a separate input means. The touch by the finger and the touch by the pen can be differentiated from each other with this configuration, which enables the proximity sensing function and the palm rejection function. In addition, while the most important thing is that the pen can be implemented in a small size since touch inputs of various levels can be differentiated from each other, the EMR type pen requires an input means for recognizing a plurality of coordinates.
An EMR type stylus pen input device is capable of detecting an inclined angle and an inclined direction by using two coils in hardware.
Whereas, an EMR type stylus pen input device using a single coil cannot measure the inclined angle and the inclined direction. Thus, there is a restriction in that a stylus pen or writing brush effect using the device cannot be variously used. Further, a coordinate error is caused when the tip of the stylus pen and the coil are deviated in position from each other.
In this case, in the conventional EMR type stylus pen input device using a single coil, it is necessary to discriminate a left hand and a right hand according to a setting and to confirm rotation information of a screen using a gravity sensor (G sensor). Through this, it is necessary to additionally correct an offset table of each coordinate region according to a characteristic of an EMR sheet having a coil array so as to correct an inclined angle.
There are eight tables in total according to the setting of left and right hands and the screen rotation, and the values forming the tables are composed of the values additionally corrected from values of inclined angles which are generated when a standard grip is performed using the left hand/the right hand in each of the coordinate regions, which are divided in order to correct a distortion caused by the EMR sheet.
In correcting an inclination error, however, when a pen input is performed in a direction where the rotation information is incorrect or is not coincident with a rotation since the touch screen device is laid in a horizontal direction in relation to a ground, there is a problem in that a value, in which a correction value is added to an error caused by an inclination, is generated as a coordinate error.